Made by Negretti & Zambra in the early 20th century, this high altitude pocket barometer is signed 'Compensated. Negretti & Zambra, LONDON.

1340' on the aluminium dial and has a barometric scale ranging from 17 - 31 inches, with a rotating altimeter scale for altitudes up to 16,000 feet.

Although the nickel plating is a little tarnished on the underside, the barometer is in full working order, passing the plastic bag test with the needle rising and falling under pressure, and is set by rotating the back plate rather than with the more common adjustment screw.

Primarily intended for mountaineering activities, this instrument from a renowned maker measures 50mm in diameter, not including the hanging ring, by 18mm in depth and weighs just under 150 grams with its black leather case.